1. Field
The present disclosure relates to a dielectric ceramic composition capable of ensuring X8R or X9S temperature characteristics and reliability, a multilayer ceramic capacitor containing the same, and a method for manufacturing a multilayer ceramic capacitor.
2. Description of Related Art
In general, electronic components using a ceramic material, such as capacitors, inductors, piezoelectric elements, varistors, or thermistors, and the like, include a ceramic body formed of the ceramic material, internal electrodes formed in the ceramic body, and external electrodes installed on a surface or surfaces of the ceramic body to be connected to the internal electrodes.
Among ceramic electronic components, a multilayer ceramic capacitor includes a plurality of stacked dielectric layers, internal electrodes disposed to face each other with respective dielectric layers interposed therebetween, and external electrodes electrically connected to the internal electrodes.
Multilayer ceramic capacitors are widely used as components in mobile communications devices such as computers, personal digital assistants (PDAs), mobile phones, or the like, due to advantages thereof such as a small size, high capacitance, ease of mounting, and the like.
In general, a multilayer ceramic capacitor is manufactured by stacking layers of a conductive paste used for forming an internal electrode and a paste used for forming a dielectric layer using a sheet method, a printing method, or the like, and simultaneously sintering the stacked layers of paste.
Recently, with the increase in use of electronic control devices in vehicles and the development of hybrid vehicles and electric vehicles, demand for multilayer ceramic capacitors capable of being used at high temperatures of 150° C. or more has gradually increased.
Currently, as a dielectric material capable of being sintered under a reduction atmosphere and being applied to a product capable of ensuring characteristics up to 200° C., there is provided a COG-based dielectric material, but permittivity thereof is 30 or so, significantly low, such that it is difficult to manufacture a high capacitance product.
In a case of BaTiO3, permittivity is high (1000 or more), but the permittivity is rapidly decreased at a Curie temperature of 125° C. or more, such that it is impossible to maintain device characteristics up to 200° C., higher than 150° C.
In order to increase the Curie temperature of BaTiO3, a method for solid-dissolving Pb in a Ba-site is used, but Pb is classified as a material subject to environmental regulations, such that there is a large limitation in using Pb.
In addition, it is known that materials such as Bi(Mg0.5Ti0.5)O3, (Bi0.5Na0.5)TiO3, Bi(Zn0.5Ti0.5)O3, BiScO3, and the like, perovskite materials containing a BaTiO3 material and Bi, may provide stable permittivity at a high temperature while increasing a Curie temperature, but these materials may only be sintered under an air atmosphere.
That is, in a case of manufacturing a multilayer ceramic capacitor including Ni internal electrodes using materials such as Bi(Mg0.5Ti0.5)O3, (Bi0.5Na0.5)TiO3, Bi(Zn0.5Ti0.5)O3, BiScO3, and the like, at the time of sintering under a reduction atmosphere, insulation resistance is rapidly decreased, such that it is difficult to use these materials.
As a dielectric material of a high-temperature capacitor capable of being sintered under a reduction atmosphere, Na (Nb, Ta) O3 has been used. However, since Nb and Ta (starting materials of Na(Nb,Ta)O3) are expensive, costs of Nb and Ta account for a large portion of material costs at the time of mass-production, and insulation resistance characteristics may be deteriorated as compared to BaTiO3.
In addition, BaTi2O5, is known to have a Curie temperature of about 500° C., but BaTi2O5 also has problems in that BaTi2O5 may only be sintered under an air atmosphere, and reduction resistance and insulation resistance may be deteriorated.
Therefore, there is a need to develop a dielectric material capable of implementing normal insulation resistance while having a Curie temperature higher than that of BaTiO3, even in a case of being sintered under a reduction atmosphere.